1. Field of the Invention
The present invention relates to radio frequency (RF) transponders and radio frequency identification (RFID) systems, and more particularly, to a system and method of using at least one identification number to effectuate communication between an RF transponder and an RFID base station.
2. Description of Related Art
In the automatic data identification industry, the use of RF transponders (also known as RF tags) has grown in prominence as a way to track data regarding an object on, which an RF transponder is affixed. An RF transponder generally includes a semiconductor memory in which information may be stored. An RF base station containing a transmitter-receiver unit is used to query an RF transponder that may be at a distance from the base station. The RF transponder detects the interrogating signal and transmits a response signal containing encoded data back to the base station. RF and RFID systems are used in applications such as inventory management, security access, personnel identification, factory automation, automotive toll debiting, and vehicle identification, to name just a few.
Such RFID systems provide certain advantages over conventional optical indicia recognition systems (e.g., bar code symbols). For example, the RF transponders may have a memory capacity of several kilobytes or more, which is substantially greater than the maximum amount of data that may be contained in a conventional one-dimensional bar code symbol. The RF transponder memory may be re-written with new or additional data, which would not be possible with a printed bar code symbol. Moreover, RF transponders may be readable at a distance without requiring a direct line-of-sight view by the interrogator, unlike bar code symbols that must be within a direct line-of-sight and which may be entirely unreadable if the symbol is obscured or damaged. An additional advantage of RFID systems is that several RF transponders can be read by the interrogator at one time.
RF transponders may either be “read-only” (R), in which data can only be read from the RF transponder, or “read/write” (R/W), in which data can both be read from and written to the RF transponder. In R/W RF transponders, the memory is typically divided into two sectors—a first sector that is “write protected” and a second sector that is not. Data that is stored in the second sector is allowed to be erased or overwritten. The first sector general includes information that should not to be erased, such as the RF transponder's identification (ID) number and the like.
The traditional method of writing data to a R/W RF transponder is to first interrogate the transponder to determine its ID number. The ID number is then used by the RFID base station to identify the transponder (e.g., to determine whether a write request can or should be transmitted, etc.) and to construct a proper write request. This is because a write request general includes (i) a write command (or opcode), (ii) an address of a memory device, (iii) data to be stored at that address, and (iv) the ID number of the RF transponder at issue. The RF transponder's ID number is an important component of the request in that it allows the RF transponder to determine which transponder the request is directed toward. In other words, if the ID number included in the write request does not match the ID number stored on the RF transponder, the request may be ignored by the transponder.
A drawback of such a communication method is that an ID number is typically large, and therefore increases the amount of time it takes to perform a write operation. This is because the (large) ID number needs to be retrieved from memory, transmitted to the RFID base station, incorporated into the write request, and transmitted back to the RF transponder. The ID number needs to be large, however, to provide sufficient discrimination between a large number of RF transponders (or objects attached thereto).
Accordingly, it would be very desirable to provide a system and method of communicating with an RF transponder that shortens the amount of time it takes to perform a write operation. It would also be very desirable to do so without decreasing (at least substantially) the number of RF transponders that can be identified.